*     might be the keys' natural order)
     * @since 31.0
     */
    @Override
    @SuppressWarnings("unchecked") // see inline comments
    public ImmutableSortedMap<K, V> buildOrThrow() {
      switch (size) {
        case 0:
          return emptyMap(comparator);
        case 1:
          // We're careful to put only K and V instances in.

    @GuardedBy("lock")
    private int runningTasks = 0;

    @GuardedBy("lock")
    private boolean shutdown = false;

    @Override
    public void execute(Runnable command) {
      startTask();
      try {
        command.run();
      } finally {
        endTask();
      }
    }

    @Override
    public boolean isShutdown() {
      synchronized (lock) {
        return shutdown;

        return new Thread(r);
      }
    }

    public static final class DummyExecutor implements Executor, Serializable {
      @Override
      public void execute(Runnable command) {}
    }
  }

  private static final class NullByteSink extends ByteSink implements Serializable {
    private static final NullByteSink INSTANCE = new NullByteSink();

    @Override

        return new Thread(r);
      }
    }

    public static final class DummyExecutor implements Executor, Serializable {
      @Override
      public void execute(Runnable command) {}
    }
  }

  private static final class NullByteSink extends ByteSink implements Serializable {
    private static final NullByteSink INSTANCE = new NullByteSink();

    @Override